My understanding is that in North America FM radio is horizontal polarization. If one cannot install an outdoor antenna perhaps one on the ceiling that is painted the same colour as the ceiling will help hide it, or an atic if possible.

I'm not sure that all stations are.

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"Some lures are designed to catch fish, others are designed to catch fisherman."

The antenna wizards hang out at Hugh Thompson's Digital Home .. It is a great resource for multimedia home entertainment. The Toronto/Buffalo region is like a "big bowl" so I can receive all the UHF tv stations using a small fractal antenna. But CTV moved down to channel 9 which I don't get on the fractal. For CTV, I have a loop about the size of a bicycle wheel hung on the wall. The loop is made from an extension cord with the sockets cut off and the 75ohm balun attached to the plug. Something like that will work for FM radio.

I'm in love with the Moxon antenna. Never tried one for 75 ohm though, but according to this link: http://www.moxonantennaproject.com/f...%20Antenna.pdf it's doable.
No need to use plastic pipes, I use a wooden frame, and for indoor use, it's more than enough.
It doesn't take much time to make one, and the result is well worth it.
Good luck with Your Dx'ing

For broadcast reception you can often get away without a balun. The skeleton biconical linked from an earlier post can get some balun action by leading the coax cable away between the arms of the lower element. Not as good balun action as a full biconical, but that would be a bit large for indoors!

My understanding is that in North America FM radio is horizontal polarization.....I'm not sure that all stations are.

In the US all FM radio stations used to transmit with a predominantly horizontal polarization. The transmitting antennas are multi bay arrays. The common practice was to tilt or rotate one or more bays to improve reception with vertically polarized car radio antennas. That is still the case for older station equipment.

Today most new broadcast installations employ hybrid antenna systems using a combination of vertical, horizontal and even circular polarity. This is done to offset the loss between horizontally polarized home receiving antennas and vertically polarized car radio antennas. Some information about FM transmitting antennas can be found here:

It is highly possible that the best polarity at the receiving end may not be perfectly horizontal. My experience in South Florida is that the strongest signal is usually received with a horizontal antenna, but it may be possible to reduce troublesome interference by tilting the antenna to reduce reception of the interferers signal. We have a lot of pirate broadcsters that radiate all sorts of random junk, but most seem top be vertical.

My experience has all been done with outdoor antennas and good measuring equipment. Indoor antennas will require much more experimenting since the signal strength can vary a lot with a small change of antenna position, especially in a concrete and steel building.

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AM MW ground wave is essentially vertical polarisation. We were talking about VHF FM. In the UK this started horizontal for best high quality long-distance propagation to fixed roof antennas, then added some vertical to help the majority who wanted portability and were not interested in quality.